1. Field of the Invention
The embodiments of the invention are directed to align marks for a stereoscopic image display apparatus and an alignment method and system for a stereoscopic image display apparatus using the align marks.
2. Discussion of the Related Art
Stereoscopic image display apparatuses display 3D images using a stereoscopic technique or autostereoscopic technique. The stereoscopic technique resorts to using parallax between left and right eyes, and may or may not use specific glasses to provide a 3D effect. When using the specific glasses, as a direct-emissive type display device or projector displays left and right images with their polarization direction changed or in a time-division manner, a viewer sees 3D images through polarization glasses or shutter glasses. With no glasses, optical parts, such as a parallax barrier or lenticular lens, are installed in front of or behind the display screen to separate the optical axes of the left and right images.
In the 3D image implementations adopting polarization glasses, a polarization separation element, such as a pattern retarder, is required to be attached on the display panel. The pattern retarder renders the polarization of the left and right-eyed images displayed on the display panel to be different from each other. When watching a 3D image displayed on the stereoscopic image display apparatus using polarization glasses, a viewer feels left-eyed image polarized light through a left-eyed filter of the polarization glasses and right-eyed image polarized light through a right-eyed filter of the polarization glasses, thereby perceiving a 3D effect.
The shutter glasses-type stereoscopic image display apparatus, however, alternately displays left and right-eyed images on the display panel and opens the left and right shutters of the shutter glasses in synchronization with the left and right-eyed images, respectively, without use of a polarization separation element. A viewer sees the left-eyed image through the left shutter and the right-eyed image through the right shutter, thereby perceiving a 3D effect. Despite no need of any polarization separation element, the shutter glasses-type stereoscopic image display apparatus suffers from high price due to expensive shutter glasses. From the point of view of 3D image quality, the shutter glasses-type stereoscopic image display apparatus is disadvantageous because the left and right-eyed images are subjected to time division with a predetermined time interval, which increases flicker and 3D crosstalk compared to the polarization glasses-type display apparatus, thereby leading to an increase in viewers' fatigue. The “flicker” refers to a phenomenon in which brightness of an image displayed on the display panel fluctuates at a constant time interval. The “3D crosstalk” refers to a viewer perceiving the left and right-eyed images displayed on the display panel with a single eye (left eye or right eye) at the same time, so that the user perceives overlap of the images.
In the shutter glasses-type stereoscopic display apparatus, each of the left and right shutter needs to be electrically opened/closed in synchronization with the display panel. For this purpose, the shutter glasses include a synchronization circuit for opening and closing the left and right shutters. The synchronization circuit includes an infrared (IR) receiving circuit, a driving voltage switching circuit, or the like. For this reason, the shutter glasses-type stereoscopic image display apparatus requires high-cost shutter glasses. The shutter glasses generate electromagnetic radiations.
Because of use of low-cost polarization glasses, the polarization glasses-type stereoscopic image display apparatus enjoys a lower price than that the shutter glasses-type stereoscopic image display apparatus in spite of requiring a polarization separation element to be attached onto the display panel. In the polarization glasses-type stereoscopic image display apparatus, the left and right-eyed images are simultaneously displayed on the display panel and are split on a per-line basis, so that a lower degree of flicker and 3D crosstalk occurs than when a 3D image is realized by the shutter glasses-type display apparatus, thus reducing fatigue that a viewer may feel.
The pattern retarders are classified into glass pattern retarders (GPRs) in which a pattern retarder is formed on a glass substrate and film pattern retarders (FPRs) in which a pattern retarder is formed on a film substrate. The film pattern retarders are more advantageous than the glass pattern retarders because of ability to reduce thickness, weight, and prices of the display panel. Accordingly, research on the film pattern retarders is intensively ongoing.
In the polarization glasses-type stereoscopic image display apparatus, accuracy in alignment between the pattern retarder and display panel has a significant influence on price, productivity, and 3D image quality. According to a conventional method of aligning the pattern retarder with the display panel, align marks AM1′ to AM4′ are formed on the display panel PNL and align marks AM1 to AM4 are formed on the pattern retarder PR as shown in FIG. 1, and the display panel PNL is attached onto the pattern retarder PR while the display panel PNL and the pattern retarder PR are aligned with each other so that the align marks AM1 to AM4 conform to the align marks AM1′ to AM4′ along a vertical direction.
A separate process is required in manufacturing the pattern retarder PR to form the align marks AM1 to AM4 on the pattern retarder PR.
The align marks AM1 to AM4 need to be formed while the substrate (or film) of the pattern retarder PR remains stationary, which the manufacturing process of the pattern retarder PR cannot be performed continuously, thus resulting in a delay for process time.
Along with the align marks AM1 to AM4, patterns are formed on the pattern retarder PR to be opposite to pixels of the display panel PNL in order to separate polarization characteristics of the left and right-eyed images. A misalignment can occur between the patterns of the pattern retarder PR and the align marks AM1 to AM4. Under this circumstance, even when the align marks AM1 to AM4 of the pattern retarder PR are precisely aligned with the align marks AM1′ to AM4′ of the display panel PNL thanks to an alignment error between the align marks AM1 to AM4 and patterns of pattern retarder PR, an alignment error ends up created between the patterns of the pattern retarder PR and the pixels of the display panel PNL.